centre for materials engineering · bsc(hons) students registered vs students graduated (2012 -...

CENTRE FOR MATERIALS ENGINEERINGDepartment of Mechanical Engineering

REVIEW REPORT - JUNE 2018

CME REVIEW REPORT - JUNE 2018

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S Self review portfolio

1: Descriptive Information

1.1 Introduction

1.2 Nature of research activities

1.3 Summary of research activities since the last review (2012 - 2017)

1.4 Current and future research activities

1.5 Management of research activities

1.6 Sustaining and developing an active and vital research culture in the unit

1.7 Research infrastructure and facilities

1.8 Interdisciplinary and collaborative research

1.9 Staff and succession planning

1.10 BSc(Hons) in Materials Science programme

2: Quality of research output

3: Research capacity development

List of Masters ProjectsBSc(Hons) students registered vs students graduated (2012 - 2017)Journal publications. Refereed conference proceedings and extended abstracts

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CENTRE FOR MATERIALS ENGINEERING

Self review portfolio

June 2018

Academic Staff Members

Professor RD Knutsen (Director)Dr SL GeorgeDr CD WoolardProfessor RB Tait (Emeritus)

Contract Support Staff

Dr RJ Curry (Senior Research Officer)Dr JE Westraadt (Senior Research Officer hosted at Nelson Mandela University)Mrs PM Louw (Senior Technical Officer)Mrs S von Willingh (Scientific Officer)

Guest Researchers and Lecturers

Ms T Rampai (UCT Chem Eng Dept) Dr M Topíc (iThemba LABS – now retired)Dr T Becker (Mechanical and Mechatronic Engineering, Stellenbosch University)Dr RA Ricks (Technology Strategy Consultants, UK)Dr P Evans (Technology Strategy Consultants, UK)Mr M Shirran (Consultant)

Physical Address

Centre for Materials EngineeringDepartment of Mechanical EngineeringLevel 2, Menzies BuildingLibrary RoadUpper CampusRondebosch

Tel: 021 650 3173 / 4959Email: [email protected]


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1: Descriptive Information

1.1 Introduction

The Centre for Materials Engineering, which is an integral part of the Mechanical Engineering Department since 2000, was established (originally as a Faculty department) in 1972 and has the objectives of educating and training students in the broad field of materials science and engineering through focused research activities at BSc(Hons), MSc and PhD levels. At a fundamental level we are concerned with the physical, chemical, electrical and mechanical properties of ceramic, polymeric, metallic and composite materials and as such we have developed appropriate infrastructure and test facilities to support this activity. Furthermore, our staff complement, including permanent, contract, and visiting personnel, are highly skilled in providing teaching, research and technical support to students, our sponsors, and academic and industry collaborators.

Our mission is to use research as a vehicle to develop human capacity through postgraduate enrolment and we promote quality and relevant research through liaison with local and international research partners, industry and government initiatives. The Centre also provides critical infrastructure and input to support the thriving mechanical engineering and mechanical and mechatronic engineering undergraduate programmes that are offered in the Mechanical Engineering Department.

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1.2 Nature of research activities

The nature of research activities undertaken in the Centre for Materials Engineering at UCT is defined in the following contexts:

• The development and growth of a sustainable and competitive manufacturing industry in South Africa is contingent upon developing and nurturing expertise in materials science and engineering, with specific attention directed towards materials in manufacturing. In view of this it is important that materials research is integrated into a multi-disciplinary approach towards strengthening manufacturing and product technologies. As such, the research activities must provide a platform to develop appropriate human resources that can underpin a developing manufacturing economy in South Africa. These needs are addressed by integrating multiple research projects into a single ongoing theme, namely, materials in manufacturing.

• Safe and sustainable engineering practice requires expert knowledge of the performance of materials during service, the ability to assess remnant life, and the expertise to institute remedial action as appropriate. Whilst our Centre has historically been involved in extensive studies with respect to the tribology of materials and engineering systems, our current focus has been extended to include high temperature strength and creep performance, fatigue and fracture, and corrosion and chemical degradation of materials. In this regard, our research is directed at supporting, where possible, the chemical, energy, mining, construction and marine industries in South Africa. The most dominant in terms of current activities is the involvement and support provided by the Eskom Power Plant Engineering Institute (EPPEI). The EPPEI Materials and Mechanics Specialisation is hosted in our Centre since 2012 and we are presently in the Phase II cycle which continues until the end of 2021. Our contributions to the EPPEI programme, which include skills advancement for Eskom engineers, technical support for Eskom operations, and research and development for improving component life cycle management, is extensive and involves substantial collaboration with other academic institutions in South Africa.


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1.3 Summary of research activities since the last review (2012 - 2017)

1.3.1 Research collaboration with the Department of Science and Technology supported Titanium Centre of Competence

One of the main research thrusts at the Centre for Materials Engineering at UCT is aimed at addressing the need to develop competitive niche areas in the production and application of light metal alloy products for the transport, medical and chemical industries. This involvement is driven by the strategy of the Department of Science and Technology (DST) to promote industry development in light metals, and most specifically, within the area of titanium metal alloy process and product development. The Titanium Centre of Competence (TiCoC), which is hosted by the CSIR, has been established by the DST and the broad aim of the TiCoC is to promote a vibrant titanium industry in South Africa that will capitalise on the mineral and energy resources in South Africa, and lead to significant value-added product development and manufacture for the international market.

The Centre for Materials Engineering at UCT provides crucial support to the TiCoC in which our role focuses on the optimisation of titanium alloy properties through the process of tailoring the metal’s composition and microstructure. Key to the development of the latter is the thermo-mechanical processing of the metal in such a way that the bulk shape and internal microstructure (or nano-structure in some cases) are modified to meet the end-user requirements. Consequently, the study of the relationships between thermo-mechanical process and metal structure evolution is important. Furthermore, we have also focused on powder metallurgy process routes, and specifically direct powder rolling, to take advantage of potentially cheaper supply of titanium metal via direct reduction to produce powder.

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1.3.1.1 Process Development for the Production of Ti-6Al-4V Flat Product via Direct Powder Rolling, Hot-roll Densification and Grain Refinement

There are strong indicators world-wide that titanium powder will increase in prominence in the total beneficiation value chain and that titanium component production via the powder process route will compete to a much greater extent with the conventional liquid metal/ingot route. The strong driver in this regard is the promise demonstrated by recent advances in direct powder reduction as opposed to the conventional (and highly energy intensive) Kroll process. This situation is even further supported by recent progress in the development of the local CSIR-Ti process, which claims to offer a more efficient (and economical) continuous process to reduce TiCl4 to metal powder. As a result of the more cost effective direct powder reduction route, it is highly likely that mill (commodity) products will increasingly be produced via direct powder rolling (DPR) processes as opposed to the liquid metal/ingot/rolling route. This development will create opportunities to build new industries in South Africa for titanium metal production.

The DPR process is by all accounts a new technology despite the fact that it was first proposed in the 1960’s. Although a patent (US Patent 7,311,873 B2) was re-launched quite recently, the DPR process still requires considerable development in order to optimise the production of plate and sheet product and to ensure that the process will be competitive with the conventional ingot metallurgy process route. In particular, the inclusion of a high temperature sinter (1200ºC) at the end of the DPR process eliminates the potential to produce fine grained mill products for good toughness and fatigue strength. Consequently, our proposed research approach considered modifications to the DPR process that will attempt to avoid the final high temperature sinter step and promote grain refinement by deformation processing.

Our initial approach to direct powder rolling was to gain experience in producing metal strip (i.e. cold compaction by rolling). To this end a new purpose built mini-rolling mill was purchased from China and successfully installed and commissioned in the UCT Centre for Materials Engineering. The approach to successfully producing metal strip was initially explored using austenitic stainless steel powder in order to minimise costs during the early trials. The stainless steel powder was chosen in view of its similar mechanical properties to CP-Ti powder. Trials resulted in the development of an appropriate hopper feed system, guiding channels to constrain strip width, and roll out system to protect the strip on exit from the rolling mill. The initial trials enabled the production of stainless steel strip widths from 50-70mm and strip thickness from 2-3mm. Similar results were obtained for the CP-Ti powder although considerable differences were experienced in terms of strip density in the green (compacted) state. A full parametric study was completed which measured the strip density, strip width, strip green strength, rolling limits amongst other properties for the CP-Ti powder. In parallel, the powder properties were characterised, with the assistance of the CSIR Light Metals Division, and rolling simulations were performed using the Johanson model. The simulations were compared with the actual experimental rolling data which allowed the limits of the existing rolling mill to be identified. This exercise greatly assisted the CSIR Light Metals Division in reaching agreement on the specification of a larger rolling mill which has also been purchased from the same supplier in China. This mill was ordered by the CSIR early in 2015. A detailed account of the development of the simulation model according to the Johanson theory and the comparison with our experimental direct


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powder rolling results was included in a successful MSc dissertation (2015). In addition, we were able to produce final CP-Ti metal strip, which after cold rolling and annealing, demonstrated tensile mechanical properties in the same range as wrought CP-Ti. This research is being followed up by extending the work to include Ti-6Al-4V powder blends.

In parallel to the optimisation of the laboratory direct powder rolling process, the influence of hydrogen on compaction and sintering of Ti-6Al-4V was studied. The compactability of the various Ti/TiH2 powder mixes and the green strength of the compacts has been established. Notwithstanding the expected influence of TiH2 on density, in this particular case it appears that the difference in particle size between the CP-Ti powder and TiH2 has greater influence on density development. This is somewhat unfortunate, but it does nevertheless highlight the important influence of bimodal particle size distributions. Sintering trials for the various Ti/TiH2 powder mixes in argon, argon/hydrogen, and vacuum have revealed surprising behaviour at the lower 1050°C sintering temperature. In this case high porosity levels are detected when sintering occurs in the argon/hydrogen atmosphere. This is particularly evident for the Ti-6Al-4V alloy composition. Experiments are currently underway to investigate this peculiar behaviour which could be deleterious when TiH2 powder is utilised instead of CP-Ti powder.

Whilst we have invested substantial effort into researching the DPR process with a view to establishing a technology pack that will promote the production of DPR strip metal in competition with conventional ingot metallurgy processes, we determined that it was incumbent on us to also more closely investigate the commercial viability of producing titanium strip metal via the DPR route based on practices already established in the open literature. To this end, we recruited an industrial engineering graduate to pursue an MSc project aimed at a critical review of the commercial feasibility of direct powder rolled titanium. A commercial viability assessment of DPR was structured around three analyses: 1.) whether a supply-side market exists to support a commercial enterprise, 2.) how the performance of DPR product compares to the performance of product produced via the conventional wrought route, and 3.) what range of potential product applications could be suitable for DPR product. A systematic review of published research was conducted by extracting and consolidating performance and process data, and a market analysis was conducted by sourcing price points from powder suppliers and wrought product suppliers.

The performance of DPR product, in terms of elongation and ultimate tensile strength, was found to be comparable to the typical properties of ASTM grade 3 and 4 wrought product, which contain higher oxygen and are the least ductile of the commercially pure titanium grades. Due to the particulate nature of the starting stock and titanium’s affinity for oxygen, oxidation was found to be the single greatest problem in powder metallurgy. The upper and lower bounds of the oxygen range were identified, and the consolidation of data showed that an oxygen content of less than 0.2 wt% is not commonly achieved for non-hydride derived product. The possibility of producing a weldable product via DPR was found to be poor, due to the unacceptable degree of chlorine content, which is typically greater than 0.02 wt% in low-cost (non-melt) commercially available powders, as well as the fact that weldability has not been reliably demonstrated for powder metallurgy product made from these powders. The existing powder market was also found to be inadequately geared towards supporting a commercial enterprise due to the small size of the market and the lack of availability of low-cost quality powders. The comparison of

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powder prices to wrought product prices showed that the potential for commercial viability is likely to exist only for thin gauge strip of less than 1mm thickness, as this is where cost savings can be attained through direct route processing.

Based on the DPR product profile identified, the range of potential product applications was found to be greatly limited. The inability to reliably meet the typical properties of the “workhorse”, grade 2, excludes the largest proportion of applications for which pure titanium in strip form is used (heat exchangers and tubing). Furthermore, the lack of evidence of adequate weldability further restricts the usage of DPR product to applications where welding is not a critical requirement. For these reasons, it was concluded that DPR is not a commercially viable process.

1.3.1.2 Grain refinement and mechanical property optimisation in cast titanium alloys by thermo-hydrogen processing.

Thermo-hydrogen processing (THP), which involves temporary alloying of titanium with hydrogen, provides opportunities to optimise the thermo-mechanical processing of titanium alloys by way of modifying slip behaviour during plastic deformation with resultant drop in mechanical loads and process temperature. Besides making the mechanical working process easier, temporary alloying with hydrogen also contributes to grain refinement and hence offers opportunities for improving the microstructure of castings either for net shape applications or further shaping by forging. To this end, the main objective of the study is to establish THP and deformation processing parameters that will lead to refinement of cast microstructures in the Ti-6Al-4V alloy.

A comprehensive PhD study uses hydrogen processing (temporary hydrogen alloying) to refine the coarse 2000µm diameter cast Ti-6Al-4V grain sizes to submicron level (less than 1µm). The PhD study has been focussed on understanding microstructure evolution during hydrogen processing and to evaluate the mechanical performance of hydrogen-refined microstructures. The initial thought on mechanical performance, and supported by substantial research in the open literature, was that refined microstructures yield improved tensile mechanical properties (higher strength and ductility due to the significant grain refinement). To this end, simulated as-cast microstructures were produced by heat treating wrought Ti-6Al-4V material to super-transus temperatures to grow the beta grain size up to approximately 2000µm in diameter. This material was used as the point of reference for subsequent THP/dehydrogenation processing and mechanical property assessment. However, an extensive matrix of tensile tests (using a range of THP and dehydrogenation parameters) revealed that phase morphology and composition also affected tensile performance besides the grain size. Hydrogen processing not only refined the grain size, but it also promoted significant precipitation of the brittle Ti3Al phase that depreciated tensile performance. The PhD study has progressed towards finding ways to retain the benefit of hydrogen-assisted grain refinement but avoid its concomitant Ti3Al embrittlement. In doing so, substantial effort has been directed at understanding the role of hydrogen in promoting grain refinement. In particular, the phase transformations and associated element partitioning have been studied using advanced EBSD and high resolution transmission electron microscopy. It is evident that the formation of titanium hydrides during the hydrogenation step leads to aluminium enrichment in the α-phase and subsequent formation of Ti3Al. Although the THP/dehydrogenation process has now been tailored to dissolve the Ti3Al precipitates, with concomitant improvement in tensile strength and


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ductility, the study continues to investigate the possibility of minimising the formation of Ti3Al in the first instance whilst retaining the ability to refine the grain structure.

1.3.1.3 Hot deformation processing of CP-Ti and Ti-6Al-4V

Titanium and most of its alloys undergo allotropic phase transformations during heating and cooling. These solid state phase transformations influence the strength of the metal and the mode of deformation and resultant microstructure evolution. Whilst basic knowledge concerning this behaviour is widely known, there is very limited information accessible in the open literature that addresses the detailed relationships between high temperature deformation processing, microstructure evolution and mechanical property development. For the most part this position may be due to the fact that titanium and its alloys are produced in much lower volumes than wrought metals such as aluminium and steels. Nevertheless, it is anticipated that there will be significant growth in the titanium industry and hence the need arises to develop better predictive tools in order to relate thermo-mechanical processes to microstructure and mechanical property development. The objective of our research has been to systematically map out the microstructure (and mechanical properties) development in Ti-6Al-4V as function of strain, strain rate and deformation temperature with a view to establishing process limits, particularly with respect to strain rate which is reported to cause microstructural instabilities at strain rates greater than 1s-1. A range of hot compression tests have been performed in the strain rate range from 1s-1 up to 50s-1 and at temperatures from 750-1050°C. The microstructures and textures have been studied using SEM-EBSD and X-ray diffraction.

The results of this work have shown a close relationship between strain rate sensitivity and volume fraction of α phase. For the deformation tests conducted in the β phase field (1050°C), the increase in the strain rate does not result in significant changes in the microstructure and texture characteristics. In this case, the strain can be easily accommodated due to the high number of active slip systems in the bcc crystal structure, and microstructural defects are promptly reduced by the mechanisms of dynamic recovery and dynamic recrystallization. In the α+β phase field (950°C), the deformation behavior and consequently the texture characteristics are controlled by the ductile β phase, whereas the α grains tend to rotate to orientations where the movement of dislocations between the α/β interfaces is facilitated. Under these circumstances the increase in the strain rate prevents the reorientation of the α grains, leading to a significant decrease of the texture strength. For the tests conducted in the α-phase field (750°C and 850°C), it is noticeable that the deformation results in dynamic or meta-dynamic recrystallization of the microstructure. At low strain rate, the nucleation of small new grains is more intense and uniform, but increase in strain rate results in strain localization in regions adjacent to grains that represent hard orientations. Strain localisation may account for the formation of shear bands which further prevents the {0001}//CD grains from deforming. The latter can influence texture topology in the final product. Whilst these are significant and important findings, we have also identified that the morphology of the starting grain structure may also contribute significantly to the influence of strain rate and temperature on microstructure and mechanical property evolution. To this end, we will continue the study by preparing specimens with a range in starting microstructures and following a similar tests matrix to the previous study.

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1.3.2 Additive manufacturing of titanium alloy components: Integrity and mechanical property assessment

As part of our endeavour to support the Titanium Centre of Competence and to expand our experience in titanium alloy physical metallurgy, we embarked on a collaborative research programme with the University of Leuven in Belgium to develop competencies in the assessment of the integrity and mechanical properties of Ti-6Al-4V components produced by the selective laser melting (SLM) additive manufacturing process. The programme commenced in 2012 and was made possible by the award of an Erasmus Mundus Scholarship for International Students to a PhD student. The student spent 10 months at the University of Leuven (under the mentorship of Professor Jan van Humbeeck in the Mechanical Engineering Department) during which time the relevant components were manufactured, and the tests protocol and preliminary tests were completed. The project focussed on the investigation of the fracture toughness and fatigue crack growth rate properties of SLM specimens produced from grade 5 Ti-6Al-4V powder metal. Three specimen orientations relative to the build direction as well as two different post-build heat treatments were considered. Specimens and test procedures were designed in accordance with ASTM E399 and ASTM E647 standards.

After completing a comprehensive test matrix, both at the University of Leuven and at the UCT Centre for Materials Engineering, the results show that there is a strong influence of post-build processing as well specimen orientation on the dynamic behaviour of SLM produced Ti-6Al-4V. The greatest improvement in properties after heat treatment was demonstrated when the fracture plane is perpendicular to the SLM build direction. This behaviour is attributed to the higher anticipated influence of residual stress for this orientation. The transformation of the initial rapidly solidified microstructure during heat treatment (both super-transus and sub-transus) has a smaller beneficial effect on improving mechanical properties. The two journal publications completed, in collaboration with authors from the University of Leuven, provide clear insight into the critical need to perform post-build stress relief heat treatments and/or modify the manufacturing process to avoid (or at least minimise) the development of deleterious residual stresses.

The work was designed to continue to include detailed analysis of the relationships between microstructure morphology and crack path propagation during fatigue experiments, but unfortunately the student has withdrawn from the PhD registration with effect from January 2018 (after a period of leave of absence during 2016 and 2017). Future plans will be reviewed, and the project will most likely continue at MSc level when a suitable candidate becomes available. Nevertheless, this initially exposure to the SLM additive manufacturing process of Ti-6Al-4V components now feeds directly into our involvement in the Collaborative Programme in Additive Manufacturing consortium which is supported by the Department of Science and Technology and hosted at the CSIR-National Laser Centre.


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1.3.3 Aluminium rolled products process optimisation

1.3.3.1 Homogenisation practice and thermo-mechanical processing of AA3104 can-body stock

The metals industry in South Africa remains largely undeveloped compared to international norms. Our capacity for aluminium beneficiation is limited to a few players with relatively low tonnage outputs but the primary focus remains on wrought product manufacture. Hulamin Rolled Products in Pietermaritzburg produces a number of niche wrought products but their main tonnage output is foil product and can-end stock. In about 2012 they embarked on the production of can-body stock (CBS) which is highly challenging for their single-stand reversing finish hot mill. Although CBS is a mature product, the critical property requirements for succeeding in the high volume beverage can manufacturing industry necessitate stringent control on the homogenisation and finish hot rolling stages. Consequently we pursued an opportunity to use this challenge to broaden our skill set in thermo-mechanical processing in South Africa with a view to not only developing skilled human resource (qualified postgraduate students), but also to foster the development of a sound research base at university that is able to readily support future wrought product developments for the automotive industry.

Our initial approach proposed two project themes within the scope for developing capability for local production of CBS, namely optimisation of the homogenisation practice for the AA3104 cast slabs and secondly, laboratory simulation of the finish hot rolling of the AA3104 metal strip. The goal in both cases was to determine reliable and consistent process routes to produce CBS with appropriate microstructures and textures to guarantee the required formability for beverage can manufacture.

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1.3.3.2 Evaluation of the performance of the Gleeble 3800 thermo-mechanical facility to simulate the hot roll processes for AA3104 can-body stock

Simulation of the hot rolling practices is necessary to be able to conduct off-line trials aimed at improving the quality of AA3104 aluminium alloy sheet for producing beverage cans (referred to as can-body stock or CBS). The simulations are achieved by performing plane strain compression (PSC) testing under deformation conditions that simulate the hot mill strain, strain rate and temperature conditions. The success of the simulations is measured by being able to accurately replicate the strain, strain rate and temperature conditions in the PSC tests. The Gleeble 3800 facility provides a platform to perform simulation PSC tests although concern was raised at the time about the ability to accurately control and replicate the process temperatures. This concern is principally related to the direct resistance heating method used in the Gleeble 3800 as opposed to radiation or induction heating methods used in other simulators. The fact that aluminium is a very good heat conductor and that it has low electrical resistance is a potential threat to obtaining homogeneous temperature distribution in the PSC specimens during hot rolling simulation in the Gleeble 3800. This research project aimed to adapt the PSC specimen configuration in the Gleeble 3800 to obtain good control on temperature, strain and strain rate such that it closely approximates the actual industrial hot rolling conditions. The analysis was compared to similar PSC tests conducted using a radiant furnace heating environment at the University of Sheffield, UK.

Two different PSC test geometries were designed to evaluate the influence of specimen geometry on process temperature distribution. Systematic PSC tests were conducted at three different process temperatures and three different strain rates ranging up to 100s-1. The strain rate was varied to include the influence of adiabatic heating during the higher strain rates. In addition, the PSC test approach included single hit and multiple hit (up to 3 hits) in order to simulate and compare single hot roll pass and multiple hot roll pass events. The latter is representative of the industrial hot rolling practices. The performance of the two different specimen geometries was evaluated by comprehensive analysis of the stress – strain flow curves that developed during the deformation events. Furthermore, constitutive equation calculations were determined from the flow curve output in order to derive the material constants which describe the metal behaviour during deformation. Evaluation of the PSC output data has demonstrated a preference for a particular PSC test specimen geometry. Although it is possible to obtain reasonable output data for both specimen geometries in as much as both geometries suitably replicate the industrial hot rolling conditions, it has been demonstrated that by minimising the size of the PSC specimen, much tighter control on the temperature distribution can be achieved. The flow curve data, and in particular the derived material constants, compare very favourably with the data reported from the same test regime performed at the University of Sheffield. In addition, assessment of the strain distribution in the Gleeble 3800 PSC tests affirms the suitability of using the Gleeble 3800 to simulate the industrial hot rolling process conditions for producing AA3104 can-body stock.

1.3.3.3 Investigation of the influence of homogenisation practices on the development of intermetallic particles in AA3104 can-body stock

The microstructural evolution of AA3104 alloy during homogenisation post ingot casting is crucial for the production of high quality sheet for can deep drawing (DD) and wall ironing (WI). The microstructure


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and intermetallic particles have a direct impact on some of the key DD and WI sheet quality parameters, such as earing, tear-off and most importantly, galling resistance. During the homogenisation step a phase transformation of the intermetallic particles from β-Al6(Fe,Mn) orthorhombic phase to harder α-Al15(Fe,Mn)3Si2 cubic phase occurs. The presence of α-phase intermetallic particles is crucial for galling resistance. Ideal galling resistance requires about 1-3% by total volume fraction of all intermetallic particles, 50% of which should be the harder α-phase. In collaboration with Hulamin Rolled Products, we investigated two step homogenisation practices where the effect of the temperature of the first step is varied. The heating profiles of interest, which were guided by previous published research indicating that higher homogenisation temperature yields a better intermetallic particle phase ratio, were: Heat to 560°C (or 580°C) at a rate of 50°C per hour, hold for a 4 hour soak period, cool to 520°C and hold for 4 hour soak period, and cool to room temperature at a rate of 50°C per hour.

The objectives of this project were to initially investigate reliable testing methods to identify intermetallic particle phases and measure their volume fractions in AA3104 alloy, as the ability to quantify the particle volume fractions is essential for homogenisation parameter analysis. This has been achieved by using an image analysis process, where the source data is attained from optical microscopy and scanning electron microscopy (SEM) with electron dispersive spectroscopy (EDS), and the use of a dissolution process, the SiBut method, where the aluminium matrix is dissolved using dry butanol and only the intermetallic particles remain. These intermetallic particles are then analysed using X-ray diffraction (XRD), which allows for quantitative volume fraction analysis. The second objective was to investigate the effect of two homogenisation profiles, with varying temperatures on the evolution of the intermetallic particles. This provided quantitative data as to which homogenisation temperature profile achieved the desired particle phase volume fractions with a correct ratio of the phases. The data has shown that, while image analysis is a simple and accessible technique, there are a number of errors that can influence the volume fraction numbers. The errors result from the various thresholding steps during the image analysis process, where the distinction between the two phases and the matrix leads to an inflated volume fraction number. The higher magnification images allow for an easier phase identification process, but dispersoids and other minor phases are then included in the thresholding, while the lower magnification images make the delineation of the phases more difficult owing to their complex geometry. On the other hand the SiBut method is time consuming and a single experiment can take many hours to complete. But the quantitative data from the Rietveld peak analysis process gives reliable data, which is in line with the volume fraction numbers suggested by literature.

The research in this MSc research project has concluded that the image analysis process is a valuable technique and shows the correct trend for the phase transformation during homogenisation, but does include some unavoidable error of inflated volume fraction numbers. However, this remains a quick and easy method of establishing a trend. The SiBut method is necessary for quantitative results. Homogenisation at a higher temperature has yielded a better volume fraction ratio between the α and β phases, when following a two-step homogenisation profile.

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1.3.4 Eskom supported research specialisation in power plant materials and mechanics

Eskom established the Eskom Power Plant Engineering Institute (EPPEI) in 2012 which is represented by 8 specialisation centres at six universities in South Africa. One such specialisation is the EPPEI Materials and Mechanics Specialisation which is hosted within the UCT Centre for Materials Engineering. As set out at the beginning of Phase I (2012-2016) of the EPPEI programme, the principal objectives of the Eskom Materials and Mechanics Specialisation are to promote knowledge development in materials science and mechanics which relates to aspects of power generation in the first instance, and secondly to provide a research platform to promote the education of postgraduate candidates in focus areas that will elevate the skills levels of Eskom engineers. The seven focus areas that were identified in collaboration with Eskom at the start of the programme include (a) physical metallurgy and metallography, (b) structural integrity, (c) high temperature behaviour (including creep), (d) environmental degradation (including corrosion), (e) welding metallurgy and processes, (f) materials modelling, and (g) non-destructive evaluation (NDE). During the first 5 year phase of the programme 14 students graduated within the Materials and Mechanics Specialisation with projects that directly related to research on power plant steels. These projects range in scope from small sample test rig development and numerical modelling to material microstructural characterisation. Research areas that were addressed are creep life estimation and high temperature material damage assessment; small sample and small punch testing; weldment strain localisation measurement in the heat affected zone (HAZ); assessment of the influence of heat treatment on stress corrosion cracking resistance; modelling of diffusion and dislocation creep mechanisms in complex steel microstructures; and a fundamental study of the role of oxidation on the initiation of cracks in a pressure water nuclear reactor. The latter project involved collaboration with the Materials Ageing Institute (MAI) at EDF in France. Since this work is of interest to the MAI we were able to gain support from the MAI to utilise their simulated PWR environment to expose test coupons of AISI316 stainless steel. These exposure tests, which lasted up to 7000 hours, have enabled detailed analysis of the surface and intergranular oxide growth using advanced electron microscopy techniques. An aspect of this work was published in Corrosion Science in 2017.

The substantial support provided by Eskom, in the form of EPPEI Phase I Materials and Mechanics Specialisation, has significantly boosted the capability of the UCT Centre for Materials Engineering, both in terms of direct financial support and increased activity in steels research. The focus on weldment performance and high temperature strength has greatly expanded the use and application of our highly advanced Gleeble 3800 thermo-mechanical test facility (this facility was purchased in 2011 with a R10m grant from the NRF). Our expertise has now developed in such a way that we foresee much greater opportunity to investigate component life expectancy particularly where vulnerabilities associated with welding are concerned. Overall, the excellent health of our UCT Centre for Materials Engineering, and the strong allied mechanics support that is available as a result of being integrated into the UCT Mechanical Engineering Department, provides a strong foundation on which to build the component life cycle management thrust in EPPEI Phase II.

In addition to the research development within the UCT Centre for Materials Engineering, we have also developed a strong partnership with the Centre for High Resolution Transmission Electron Microscopy (CHRTEM) at the Nelson Mandela University. We have always placed substantial focus at the UCT


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Centre for Materials Engineering on the relationships between component properties/performance and the underlying makeup (microstructure) of engineering materials. Although we have a highly competent and well equipped electron microscope facility at UCT, we expanded our utilisation of advanced electron microscopy at the start of EPPEI Phase I by consolidating a strong relationship with the CHRTEM. This was achieved by transferring funding to the Nelson Mandela University to support the appointment of a senior research officer. During the course of Phase I the strong interaction between UCT staff, EPPEI students and CHRTEM led to rapid development of synergies in physical metallurgy (particularly relating to steels) and advanced materials characterisation using a range of electron and X-ray analytical techniques. This capability, particularly when combined with the substantive process and strength measurement capabilities at the UCT Centre for Materials Engineering, has now become an integrated part of the EPPEI Materials and Mechanics Specialisation and the attention gained from the broader Eskom enterprise is growing.

1.3.5 Corrosion research related to the off-shore oil industry

Although corrosion research is not a primary focus of our activity in the Centre for Materials Engineering, we do concern ourselves with studies that involve performance assessment in particular engineering applications. This is also very much the situation regarding our work on component life cycle management of power plant materials (the Eskom EPPEI programme which is described separately in this document). Research completed during the past five years include two investigations that were proposed by BP Angola and specifically aimed at providing postgraduate study opportunities for two of their bursars.

1.3.5.1 Assessment of the corrosion behaviour of alloys 825 and 635 in stagnant seawater: effect of temperature and welding

Alloy 825 has good weldability and generally excellent resistance to corrosion. However, for situations that require exceptional corrosion resistance, as may be experienced in the off-shore oil drilling environment, the Inconel filler metal alloy 625 is used as “overmatching composition”. But, this arrangement also raises the threat of galvanic corrosion when joining two dissimilar alloys as is the case for the alloy 825 and alloy 625 couple. In this study, the corrosion behaviour of alloy 825, alloy 625 weld metal, and the alloy 825/625 weldment have been investigated. Potentiodynamic polarization curves for the alloys were recorded in synthetic seawater across a range of temperatures (30 to 60°C). Mixed potential theory was applied to determine corrosion potentials, rates of corrosion and predict the galvanic effect of coupling alloy 825 to alloy 625 filler metal via welding. Three standard methods were considered to determine the critical pitting temperature (CPT) for alloy 825. Lastly, long-term immersion tests in seawater were conducted to determine the relationship between the laboratory accelerated test results and the performance of the alloys under real service conditions.

The results from the experimental tests revealed that alloy 825 and alloy 625 weld metal exhibit outstanding corrosion resistance to uniform corrosion, despite the effect of temperature on the corrosion rate of both alloys. The galvanic effect of coupling alloy 825 to alloy 625 via welding is insignificant. The corrosion morphology of alloy 825 and its weldment is temperature dependent. At temperatures

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below 45 °C, grain boundary attack was observed in alloy 825 samples, while pitting corrosion was observed at temperatures higher than 50°C. Alloy 625 weld metal exhibited only one mode of corrosion attack namely the selective dissolution of inter-dendritic phase throughout the test temperature range.

1.3.5.2 Development of high performance and efficient coating repair systems for offshore tropical marine environment

Rehabilitation coating of offshore equipment rarely performs as well as the original coating, despite the high cost involved. The performance gap is probably due to high relative humidity, salt contamination and limitations on the use of abrasive blast cleaning. This research project was focused on gaining a better understanding of surface preparation parameters that affect organic coating performance. Carbon steel samples were subjected to a variety of surface alterations consisting of salt contamination, mechanical wire brushing, chemical rust conversion and chemical rust removal followed by coating application and performance testing. The steel coupons were initially pre-corroded in a corrosion chamber to mimic degradation in-service. Controlled surface preparation was performed on the simulated service exposed coupons after which the new coating was applied (rehabilitated coupons).

Visual inspection and electrochemical impedance spectroscopy (EIS) was performed on the rehabilitated coupons prior to exposure and periodically during accelerated cyclic corrosion exposure for a period of 30 days. The visual condition of the coupons was used to rank the performance of the coating systems (i.e. surface preparation plus coating combination). These results were used as a benchmark to decide the optimum EIS method, which involved either phase angle at high frequency or total impedance at low frequency. The EIS method was deployed for early evaluation of the organic coating performance under the conditions studied. Furthermore, adhesion pull-off testing was performed to rank the integrity of the coating over the various prepared surfaces. It was established that salt contamination had stronger impact on the coating performance than the amount of corrosion product remaining in the surface. The outcome of this work demonstrated that the best preparation approach after pre-corrosion of the coupons was to apply rust converter to the surface before coating. Adhesion measurement was not successful on the studied coated surfaces as cohesive failure occurred on the pre-treatment layers rather than coating adhesion failure between the coating and the treated metal substrate.


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1.4 Current and future research activities

1.4.1 Research collaboration with the Department of Science and Technology supported Titanium Centre of Competence

A key focus for our ongoing collaboration with the Titanium Centre of Competence (TiCoC) is our work on titanium powder metallurgy. Notwithstanding the concerns expressed earlier in this report about the commercial viability of producing sheet product by direct powder rolling (DPR) processes, the CSIR Light Metals Division still remains optimistic about the prospect of producing titanium metal powder at lower cost than current commercial processes, and hence we continue to develop readiness to be able to provide technological input to the establishment of industrial practices. Our objective currently is to consider unique opportunities to improve the product quality and/or cost effectiveness without necessarily focusing on the powder supply. Consequently, we are continuing to direct attention at the use of hydrogen (and specifically TiH2) to promote homogenisation and densification during post-rolling sintering such that the strip product performance may move closer towards the higher alloy grades. In addition, the type of powder blends (e.g. CP-Ti + Al + V blend or CP-Ti + master alloy blend) is being considered in terms of compactability and sintering behaviour. Two MSc projects currently underway are described below.

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1.4.1.1 Optimisation of homogenisation practice for Ti-6Al-4V powder blends

The direct powder rolling practice to produce Ti-6Al-4V flat sheet is aimed at producing flat products at lowest cost and hence all avenues are explored to reduce the process cost at every opportunity. The most fundamental starting point is not to use pre-alloyed Ti-6Al-4V powders and hence steps to homogenise powder blends become critical in reducing the temperature/time combinations for heat treatment / sintering of the compacted powder sheet. An additional factor to consider is the roll compaction of the two different types of powder blends, namely (i) CP-Ti + Al-V master alloy (60Al40V), and (ii) CP-Ti + Al + V elemental powders. Although the CP-Ti + Al-V master alloy composition is more amenable to homogenisation, the CP-Ti + Al + V elemental powder mix is reported to provide better compaction due to the high plasticity of the elemental Al powder (see parallel MSc study below). A further complexity is the consideration of using hydrogenated Ti powder (TiH2) instead of CP-Ti since it has been proposed by several researchers that TiH2 assists in densification during the sintering heat treatment. Consequently there are a number of possible powder blends other than pre-alloyed Ti-6Al-4V powders that need to be considered for selection in arriving at the lowest cost process route for producing direct powder rolled Ti-6Al-4V sheet. But, ultimately a uniform composition of Ti-6Al-4V needs to be achieved throughout the material. Therefore the rate of homogenisation is required to be determined as function of heat treatment time and temperature. In addition, densification during sintering cannot be ignored since flat sheet produced by direct powder rolling ultimately has to match up to the sheet produced by conventional ingot metallurgy (liquid metal – solidification) processing routes. An additional step can also be considered in the process path which includes deformation as a means to increase density and shorten the path for diffusion thus leading to possibly more rapid homogenisation. The objectives of this project can thus be summarised as:

1. Determination of homogenisation rate for powder blends (i) CP-Ti + Al-V master alloy, (ii) CP-Ti + Al + V elemental powder, (iii) TiH2 + Al-V master alloy and (iv) TiH2 + Al + V elemental powder as function of heat treatment (sintering) temperature and time.

2. Determination of the influence of an intermediate deformation step on the homogenisation rate for the powder blends described in 1 above. Typically this could mean a process sequence such as: step 1 = sinter at temperature x and time y; step 2 = plastic deformation (pre-determined strain level) to simulate hot rolling; step 3 = final sinter at temperature p and time q. Obviously the number of step1, 2 and 3 permutations could be endless but the test matrix design would be guided by the outcome of the homogenisation rate determination in objective 1 above.

The completed MSc dissertation should provide an accurate and highly detailed assessment of the optimum powder blend/sintering process path combinations for producing lowest cost Ti-6Al-4V sheet that closely matches the microstructural integrity of sheet produced by conventional ingot metallurgy.

1.4.1.2 A parametric study of the compactability of Ti-6Al-4V during direct powder rolling

The current work compares the direct powder rolling of blended elemental powder (CP-Ti + Al + V) and CP-Ti + master alloy (Al60V40) to produce Ti-6Al-4V strip metal. Various rolling and sintering parameters are used to optimise the process and achieve strips of desirable microstructural and mechanical properties. Research is directed at comparing the green density, re-rollability of green strips, green strength, and sintered density of the two blends. In addition to the empirical analysis, the

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Johansen rolling simulation model is also being used (in a similar way to our earlier work on CP-Ti and stainless steel powders) to explore the expected behaviour of the two different blends.

A principal objective in this work is to compare the relative advantages and disadvantages of the two blends at the rolling stage and the sintering stage. It is expected that the blended elemental powder (CP-Ti + Al + V) will compact better than CP-Ti + master alloy, but that the latter might prove to sinter better (i.e. faster homogenisation and densification). Key to measuring the homogenisation rate is the development of an appropriate measurement protocol using SEM-EDS. This process was recently reported in a paper presented at the annual Microscopy of Southern Africa (MSSA) conference in December 2017.

1.4.2 Optimisation and integrity assessment of Ti-6Al-4V components produced by high speed selective laser melting

A key objective within the Department of Science and Technology (DST) supported Co-operative Programme in Additive Manufacturing (CPAM) is the development of a large capacity powder bed manufacturing system for producing Ti-6Al-4V components for the aerospace industry. In order to produce large-scale parts competitively, the laser scanning speed (or more particularly, the deposition rate) needs to be substantially increased above conventional laser scan speeds of up to 1m/s. Since the laser scan speed influences the melting and solidification rates, as well as the transient temperature profile, it is expected that microstructural features, and hence mechanical properties, will be influenced by imposing higher laser scanning rates up to 10m/s. The UCT Centre for Materials Engineering, as a principal member of the CPAM consortium, has undertaken to assess the microstructure-mechanical property relationships of components produced at laser scanning speeds within the range 1m/s – 10m/s (the test matrix is somewhat more complex in that laser power, spot size, scanning strategy, etc will also need to be considered in parallel to laser scanning speed in order to optimize the SLM process conditions). The preliminary study over the past two years has investigated samples produced using a pilot experimental setup where laser scanning speeds have ranged from 1 – 4.5m/s. Unfortunately, the experimental setup proved to be non-ideal and manifest in excessive large porosity development across the scanning speed range of interest. Our comprehensive component integrity and mechanical property assessment demonstrated that there was no correlation between scanning speed and density, fracture toughness, tensile properties and fatigue crack initiation and crack growth rate. Consequently, the study was directed at studying the role of large porosity in primarily influencing mechanical properties. In doing so we were able to establish sound methodology for the volumetric porosity analysis using micro-X-Ray tomography in collaboration with the Central Equipment Facility at Stellenbosch University which will become increasingly important in the next round of investigation. In going forward, it is planned to make use of the full-scale high capacity manufacturing system to produce test components at the required laser scanning speed range. This new approach will include an additional process variable in the form of powder bed pre-heat in order to lower thermal gradients which will influence both solidification rate and residual stress levels. Parts will be built at the CSIR-National Laser Centre using the AeroSwift platform and the cooperative research programme will involve one MSc student hosted at the UCT Centre for Materials Engineering and one MSc student hosted at the National Laser Centre. Both students will commence registration for the MSc degree at UCT in June 2018.

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1.4.3 Sustaining and further developing the aluminium industry in South Africa

The Centre for Materials Engineering has enjoyed a longstanding collaboration with Hulamin Rolled Products (Pietermaritizburg) and have undertaken many postgraduate projects on their behalf over the past 25 years, at Honours, MSc and PhD levels. During this period, the CME has established itself as the leading research centre in South Africa in the field of wrought aluminium products and processes. In addition, the CME has developed specific techniques and hardware for wrought aluminium process simulation, as well as advanced techniques for material analysis and classification. This development has been underpinned by the co-support provided by the DST Advanced Metals Initiative, and more specifically the Light Metals Development Network.

While these projects have always been conceived to address manufacturing technology of commercial relevance to Hulamin and related industry development in South Africa, they have generally been executed with the priority being to produce an academic post graduate degree, which contributes to the South African body of knowledge in aluminium production, but has not necessarily addressed specific and current technical challenges faced by Hulamin in useful industry time frames. Notwithstanding the importance of academic focus at the UCT, it is recognised that the sustainability and growth of the aluminium industry in South Africa will require all available resources to become more focused on immediate technology support and development, and that this approach will anyway have positive spin-offs for academia. To this end we have over recent months engaged with Hulamin to define a programme of technical partnership between Hulamin and the CME, which is aimed to address specific challenges faced by Hulamin in their business that they are unable to address due to the priorities of a commercial manufacturing environment, combined with a scarcity of appropriate resources, both human and equipment. This programme is intended to satisfy both Hulamin’s urgent manufacturing requirements, and an academic programme resulting in post graduate materials engineers contributing to fundamental knowledge of wrought aluminium materials. This approach will complement the existing approach of aluminium focussed content in the current BSc Honours programme.

The types of activity undertaken by the CME under the direction of Hulamin, and in collaboration with the responsible parties at Hulamin, are proposed as follows:

• Short to medium term technical assistance projects carried out by contracted post graduate staff and MSc students, with substantial input from Hulamin, to address current technical challenges within a realistic time frame.• Longer term strategic and fundamental research projects to address the understanding of metallurgical mechanisms allowing optimisation of existing products and processes, through academic based post graduate degrees (MSc or PhD) under the supervision of the experienced academic staff of the CME.• Product, alloy and process development through innovation, process simulation and material characterisation to help facilitate entry to new markets in the short or longer term, in the form of a focussed joint project between Hulamin and the CME, supplemented by academic research where required.• Competitive intelligence studies and technology reviews through the university’s extensive access to public domain literature resources, carried out by contracted post graduate staff and students.• Mechanical and material design assistance in collaboration with the Department of Mechanical Engineering.


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• Training of Hulamin technical staff through collaborative participation in process simulation and material characterisation at the CME during the execution of short term technical assistance projects.• Furthering technical education for Hulamin staff through higher degrees in relevant aluminium projects at the CME.

These activities would seek to fulfil the following goals as expressed by Hulamin:

• Resolution of urgent manufacturing challenges on an ongoing basis.• Optimisation of existing products and processes.• Growing the local body of fundamental knowledge regarding wrought aluminium manufacturing technology.• Innovative product, process and market development.• Furthering education and skills upliftment of technical staff.

Whilst this programme will certainly direct more of the CME activity towards aluminium related projects, the intention is not to remove focus from other programmes. Consequently, our proposal to Hulamin includes substantial participation from additional role players other than the core academic staff at CME.

1.4.3.1 Current and ongoing postgraduate research projects:

The main area of research is based on a collaboration with Hulamin Rolled Products. With the move to the full aluminium beverage cans in South Africa, there is now a demand for the supply of can-body stock (CBS), namely the AA3104 alloy. In most instances around the world, this sheet is produced by tandem mill hot rolling on the hot roll finishing line. However, the plant at Hulamin Rolled Products is limited to a reversing mill on the hot roll finishing line. This situation raises important challenges to ensure that the sheet product still meets the stringent requirements for can-body manufacture. To this end, we have initiated a number of projects which investigate opportunities to improve the competitiveness of the sheet produced at Hulamin Rolled Products. These projects follow on from the comprehensive study which demonstrated the ability to simulate the hot roll finishing passes on our Gleeble 3800 thermo-mechanical facility.

1.4.3.1.1 Effect of processing parameters on the microstructural evolution and texture development in AA3104 aluminium alloy during hot rolling on a reversing mill

AA3104 aluminium alloy is used for the production of can-body stock sheet material. The rolled sheet is manufactured through the hot rolling process which involves deformation at elevated temperatures. Hot deformation results in a difference in the volume fraction of the cube texture after recrystallization, hence affecting the microstructural evolution and texture development within the aluminium. An inconsistent cube texture generates positive 0/90° ears at the edges of the strip at final cold rolled gauge due to incomplete rotation of the cube texture to rolling textures. This type of earing coupled with the inconsistent cube texture is undesirable during can forming. The challenge experienced on the rolling mill is controlling texture; hence the aim of this research is to produce flat-rolled aluminium with a 10-13% recrystallization cube texture to reduce the degree of earing in the sheet product. This will be performed using plane strain compression (PSC) testing to simulate hot rolling. The desired level of

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final gauge strength, formability and surface quality, as well as the correct balance of crystallographic textures in the final product, is dependent on the processing parameters experienced during the hot rolling process.

1.4.3.1.2 The effect of homogenisation conditions on microstructural evolution during hot rolling of AA3104 aluminium alloy

AA3104 aluminium alloy is used for the production of beverage can bodies. The material produced by Hulamin Rolled Products undergoes a specific homogenisation treatment prior to hot rolling. During homogenisation there is a critical phase change of intermetallic particles, from the softer β-phase to the harder α-phase. Notwithstanding this critical microstructural feature evolution, there is also a formation of a dispersoid structure. These dispersoids are critical for particle stimulated nucleation later on in the production process. This project aims to quantify the effect of homogenisation on the dispersoid structures by installing a secondary autoclave onto the current SiBut set-up at UCT, where dry butanol is used to dissolve the aluminium matrix, leaving behind the other phases. The secondary autoclave will contain a filtration system for the separation of the smaller dispersoids. At this stage the larger α and β intermetallic particles will be filtered out in the primary autoclave, thus leaving the fragmented intermetallics and the dispersoids to be captured in the secondary autoclave. After characterisation of the effect of homogenisation practice on the dispersoid structures, samples will undergo simulated hot rolling to investigate the effect of the homogenisation practice, and intermetallic and dispersoid structures, on the evolution of the microstructure after rough rolling and finish rolling. The evolution of the microstructure will include bulk texture analysis using XRD.

1.4.3.1.3 The effect of surface condition on the roll bonding of aluminium brazing material

Clad metals are extensively used for their multi-functionality and their optimal combination of quality and cost. Roll bonding is an effective and economic processing approach to making clad metals. Roll cladding (bonding) is a solid welding technique to join dissimilar metals which is widely used as a cost-effective manufacturing technology. This technique passes a stack of dissimilar metal sheets, plates or strips through a pair of rollers to achieve proper deformation that promotes solid state bonding between the metal pieces. The roll cladding metals provide many advantages including: 1) the large area welding on the plate plane can be achieved cost-effectively; 2) roll cladding provides high production rate; 3) the multi-layer structure can be fabricated; 4) the bonding interface has a smooth continuity of material properties such as conductivity, stiffness and thermal expansion coefficient. This project focuses on the effect of the cladding and base material surface finish (R value or roughness) on the bond strength after hot and cold rolling. The roll bonding tests will be done using the Gleeble 3800, and the bond layer will be analysed with microscopy and the strength of the bond will be tested using tensile shear testing.


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1.4.4 Eskom supported research specialisation in power plant materials and mechanics

As described earlier in this document, the UCT Centre for Materials Engineering hosts the Eskom Power Plant Engineering Institute (EPPEI) specialisation in Materials and Mechanics (MM). This program is currently running in its second phase of funding which will last from 2017-2021. The Eskom fleet currently comprises of 17 power stations across the country. One of the oldest stations still in operation was built in the 1960s and it has already exceeded its design life-time by some 200%. Advances in technology have allowed engineers to improve stations beyond design performance but there is still considerable opportunity to improve life prediction and extend design performance. Eskom has also expanded its capacity by introducing two new coal-fired stations and new hydro-electric stations to their fleet which has come with its own engineering challenges and interesting research problems. Research in this programme focuses on investigating and understanding the influence of service operating environments on the performance of materials with a view to being able to (a) better predict the life of engineering materials and components in power generating plant, (b) optimise the selection of materials for plant construction, (c) improve manufacturing technologies including welding and (d) improve the reliability in monitoring material and component integrity.

During this second phase of funding the Centre has developed a comprehensive revised research strategy. The research objectives of the Materials and Mechanics Specialisation can be summarised as:

1. Determine appropriate maintenance strategies and inspection tools to be implemented on critical components.

2. Improve or advance NDT methods, techniques and analysis.3. Improve or advance welding methods, techniques and analysis.4. Develop and identify new methods or techniques for determining and performing material

characterisation.5. Develop and validate plant component modelling; microstructural, mechanical, statistical and process

should be considered.6. Advise appropriate operational plans for at risk components.

Seven new MSc student recruits in 2018 and four ongoing students (three at PhD level) are currently participating in various projects that fall into the categories mentioned above. Of the 11 students, only five are registered at UCT, three at the University of the Witwatersrand, two at Nelson Mandela University, and one at the University of Stellenbosch. This arrangement demonstrates our inter-university collaboration which is strongly promoted within the EPPEI Materials and Mechanics Specialisation. The UCT Centre for Materials Engineering is of course the academic lead and the collaboration is fostered by the full-time involvement of contract researchers at UCT and Nelson Mandela University. The collaboration allows us to draw on the strengths of other academics at these institutions who offer expertise in fields that complement the Materials and Mechanics Specialisation.

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Creep damage and weld repair

Creep damage is one of the most prevalent issues controlling the overall life expectation of a power plant. It manifests in multiple components in different ways. We are specifically investigating the effects of weld repairs on creep aged material, as well as the material parameters that affect the rate of creep damage. The latter include the influence of grain size on the creep rate and the overall ranking and performance of different steels. In welded components the Heat Affected Zone (HAZ) has been identified as a critical site needing a clear prediction of material properties specific to creep damage performance. The size of this area (1-2mm) makes it challenging to perform conventional mechanical testing on this zone in order to extract material properties or calibrate models. Consequently our aim is to develop a method to replicate the actual HAZ in a full-size homogeneous tensile creep specimen. Generally specimens of 5-10mm diameter and 30-100mm in length are needed to perform creep test. Our plan is to use the Gleeble 3800 thermo-mechanical simulator, which applies direct resistance joule heating and thereby allowing fast heating and cooling cycles, to replicate the actual welding conditions that would be experienced in the HAZ. The current difficulty is that owing to the standard configuration in the Gleeble 3800, only a central portion of the test piece is heated to the peak temperature. Our proposed solution lies in modifying the shape of the simulation specimen in the Gleeble 3800 so that it is possible to reduce the thermal gradient and thus allow for a much larger portion of the simulation specimen to undergo the thermal process that mimics the HAZ.

1.4.4.2 Stress corrosion cracking

There are currently two MSc students and a PhD student working on projects relating to stress corrosion cracking (SCC) in different power station environments. SCC can be found in many different environments such as turbine blades, pressurised pipes and storage vessels. Our current projects all have some relevance to the nuclear power industry and include the ongoing PhD project that is investigating the rate of oxidation on AISI316L stainless steel in a simulated pressure water reactor, and new MSc projects that explore the SCC resistance of duplex stainless steel weldments and the incidence of SCC failures in steam generator tubes.

1.4.4.3 Small sample testing

The extraction of small samples from critical components, either through the hydro-pillar technique or scoop sampling, provides an opportunity to obtain mechanical property data from in-service components and assemblies. This relatively new development can provide significantly more information for component life cycle management than what can be achieved through routine surface replica analysis. The hydro-pillar extraction technique has reached advanced maturity and is able to be routinely performed through the expertise provided by eNtsa at the Nelson Mandela University. Furthermore, the scoop sampling method is also currently under development by Nelson Mandela University and will be implemented in the very near future. Notwithstanding this progress, the reliability of obtaining mechanical properties from the limited volume of metal that is extracted by the hydro-pillar and scoop sampling methods remains a challenge. In particular, fracture toughness requires the determination of energy to failure which is normally measured from compact tension specimens whose geometry is required to match stringent ASTM specifications. A number of proposed procedures do exist to

1.4.4.1

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measure fracture toughness from small sample punch tests and a recent research programme has been completed by an EPPEI candidate within the Materials Science and Mechanics Specialisation at UCT which has explored a limited range of options. The purpose of the current proposed project is to further refine the small sample punch test rig and to explore and develop the analytical approach to determine fracture toughness properties that more closely match standard fracture toughness tests. This will be achieved in the first instance by further investigating the reliability of existing experimental, analytical and modeling methods to determine fracture toughness, and the outcome may then lead to modifications to the test rig to improve the reliability of measurements. Standard fracture toughness measurements will be performed in parallel to the small sample punch tests in order to assess the reliability of the test methods and corresponding data.

1.4.4.4 Computer modelling and structural integrity

The Structural Integrity group within the Physical Metallurgy Section (Eskom RT&D Division) provides Eskom with technical expertise in the areas of finite element analysis, mechanical structural integrity, code applications and interpretations, as well as fit for purpose, risk based inspection, and failure and residual life assessments required for the effective life cycle management of major components. In this research area, close collaboration with the Structural Integrity group will drive the individual research projects, which ideally will be tailored to address specific needs of the business unit to which the Eskom student is attached.

Mechanical structures and components used in the power generation industry suffer from a wide range of in service damage mechanisms including fatigue, stress corrosion cracking, creep, erosion, corrosion and embrittlement. These damage mechanisms reduce the life of these components from a safety, fit for purpose and economic point of view and need to be assessed and optimally managed in order to obtain Eskom objectives. In some cases, plant modifications for the removal of defects and/or the prevention of damage mechanisms are engineered, to code requirements where applicable, and implemented. For cases where immediate repair or replacement is not possible risk based inspection (RBI) strategies are developed after analytically demonstrating acceptable safety factors. Where such RBI strategies are employed the critical flaw sizes and required performance level of non-destructive-examination (NDE) techniques are established and specified. Although considerable finite element analysis (FEA) capabilities and experience have been developed for steady state, transient, dynamic and modal analysis which is required to obtain detailed stress, elastic and plastic strain, creep strain and vibration response information, the effect of load cycling on the life of components has not been established. The latter is increasingly becoming an important concern since the practice of load cycling on conventional power plant is almost becoming the norm. The incorporation of load cycling into computer modelling and structural assessment will be conducted in close collaboration with the Structural Integrity group at Eskom, University of Pretoria Asset Management Specialisation Centre and the University of Stellenbosch.

1.4.4.5 Erosion and wear

Erosion and wear are recognised as serious issues in a coal fired power station. The high ash content in South African coal increases the propensity for coal induced wear on the stations. The erosion

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and wear as a result of this accounts for huge losses in generating capacity throughout the fleet. An understanding of the problems and development of suitable solutions to reduce the effect specifically in the mills, burners and pulverised fuel loop are of specific interest. Furthermore, boiler tube erosion is another symptom of high ash content. Research will be performed to gain a better understanding of the mechanisms of wear, and in turn this knowledge will be deployed to select and test candidate wear resistant materials and protective systems for implementation to reduce the unplanned losses. This research is envisaged to work in close collaboration with Eskom representatives concerned with burner and mill erosion and abrasive wear, and will include collaboration with the Wits University EPPEI Specialisation centre for combustion engineering.

1.4.5 Additional research subject areas

There are some research areas which do not fall directly into the sponsored light metal and power plant component life cycle management themes, but nevertheless are important contributions to meeting development of knowledge and human capital in materials science and engineering. These projects are described below.

1.4.5.1 Investigation of the surface modification of Ti-6Al-4V to facilitate antimicrobial ionic silver integration for use in implantable orthopaedic devices

Malignant bone tumours often require the removal of large portions or the entire bone from the body of the patient. The most common location of malignant bone tumours are in the femur. The patient often comes to a point where a decision has to be made with respect to saving the limb via limb salvage surgery or complete amputation of the limb. However, there are complications with post limb salvage surgery infection. Previous studies have shown infection rates of up to 11%. The most common cause of infection is by bacterial infection. The bacteria that are most commonly responsible for post limb salvage surgery are Staphylococcus aureus and Staphylococcus epidermis.

Titanium, more specifically Ti-6V-4Al alloy, is the material of choice when it comes to limb salvage surgery. This alloy of titanium provides a favourable combination of biocompatibility, corrosion resistance and mechanical properties. The current research concerns attachment of ionic silver and silver nanoparticles to the titanium alloy to kill bacteria. A number of techniques have already been attempted, showing good results (90-100% of bacteria being killed). However, the open literature regarding these techniques is limited to studies that purely investigate the viability of the techniques in terms of antimicrobial action. i.e. the study would change the concentration of silver exposure and then a simple antimicrobial action test would be conducted and results reported in a percent of bacteria colonies killed.

Another limitation is that the studies usually do not discuss any methods by which the titanium oxide particles or nano-fibres could be attached to the metal surface. A blanket generic statement is typically given as opposed to specific experimental details. There are methods used to attach short polymers to metallic surfaces, but these often require expensive bridging molecules that cannot be commercially obtained.


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This current research aims to study the release rates of silver from the differently generated titanium metal surfaces. It also focuses on attaching titanium oxide particles and the polymer fibres to the titanium surface. A primary focus is the use of a grown oxide layer to attach the particles and fibres, which is a novel technique in this context. Thus far the results are promising. If this method proves successful, it may provide a new cost-effective method that can be used to attach polymer nanofibers and titanium oxide particles to titanium surfaces. The final stage of the research will aim to conduct in-vitro antibacterial testing in order to evaluate the effectiveness of the proposed surface modifications.

1.4.5.2 Investigation into the effect of build direction on fatigue and fracture properties of SLM Nickel-based super alloy IN718 used for the manufacture of high speed gas turbine blades

The turbine blades are often the limiting component of gas turbines. To survive in this difficult environment, where the temperatures and stresses are both high, turbine blades often use high performance materials such as superalloys, for example, the nickel-based super-alloy Inconel 713LC or Inconel 718. For certain high speed gas turbines, the blades and rotor disk are typically incorporated into a single component, the blisk. The blisk has a complex design and is typically produced through investment casting. The CSIR has designed a novel stator blisk which is proving very difficult to manufacture. For this reason they are interested in using additive manufacturing techniques to manufacture the blisks. Because of the creep resistance properties that are critical to turbines and rotors, the build direction of the additive manufacturing technique relative to the rotational axis of each blade may be critical.

This project focuses on selective laser melted nickel-based super alloy parts (an additive manufacturing process in powder metallurgy) for the blisk assembly. In order to determine the effect of build direction on mechanical properties it is necessary to perform fatigue tests to investigate how the build direction affects the fracture toughness and fatigue crack growth rates of the parts. Compact tension samples will be built and testing will cover a combination of fracture toughness and fatigue crack propagation tests of samples with different build directions. This project also involves investigating the effect of heat treatments for the removal of residual stress and promoting homogenisation, and the effect of these heat treatments on the mechanical and fatigue properties. Fractography and microstructure analysis will be performed to investigate the effect of the as-built and heat treated microstructures on the crack path during fatigue crack propagation.

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1.5 Management of research activities

For the most part, research is managed by individual academic staff members and their postgraduate research teams. Since our team members have different strengths we tend to focus on particular themes but we do often have some level of co-supervision of postgraduate students which of course promotes strong interaction. However, the Centre endeavours to embrace a broad range of materials engineering research and to this end it is important to coordinate the research activities and recruit postgraduate students to satisfy these needs. We do this by planning student project proposals that match the deliverables attached to our commitments with sponsors and recruit postgraduate students accordingly. In this way we make sure that we are able to adequately support all our postgraduate students (both in terms of bursary and project running costs), and also meet the output deliverables for our sponsors. Furthermore, important attention is given to developing and maintaining the research equipment infrastructure to ensure capacity to undertake research in a broad range of materials engineering activities. For this purpose, research generated funds and Department / University funds are pooled to enable the purchase and maintenance of appropriate equipment. Once again, we collectively plan and submit proposals for new equipment or equipment upgrades based on our need to maintain an appropriate infrastructure our broad range of activities in materials engineering research.


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1.6 Sustaining and developing an active and vital research culture in the unit

The Centre is research-focussed and highly student centric. By far the majority of our projects are designed to meet the academic requirements for MSc or PhD qualification. In addition, our sponsorship support is either driven by the agenda promoted by the Department of Science and Technology (either directly through the CSIR or indirectly through the National research Foundation (NRF)) or by technology development required by industry. In the case of the latter, we always attempt to ensure that we are able to derive tangible research level outputs in addition to shorter term solutions that may be required by the industry partner. The permanent academic staff are the main research anchor within the Centre and they are supported by contract research and technical support staff. The vibrant cohort of postgraduate students (Honours, Masters and Doctoral students) complete the research community membership.

• All our projects are associated with postgraduate student registrations and in almost all instances the registrations are fully research based (only occasionally students might register for partial course work degrees).

• Weekly research seminars are held on Friday afternoons, followed by informal interactions and discussions. All members of the Centre are expected to attend and to contribute to discussions. The research seminars are mostly presented by the postgraduate students and in some cases by academic staff and visitors. Masters and doctoral students give one or two 45-minute seminars in a given year. The BSc(Hons) students are also required to present seminars on their individual research projects to the full Centre audience.

• The preparation of research papers for publication and/or presentation at conferences is an ongoing Centre activity. Published papers are displayed prominently in the Centre.

• Postgraduate students are encouraged to publish their work whilst they are still registered. Incentives are provided through financial rewards for publishing in accredited journals or refereed conference proceedings.

• It is normal practice to facilitate attendance (including presentation) for Masters students at one or two South African conferences in the two years of their registration. We attempt to arrange for Doctoral students to make at least one international visit, at which they either carry out work in a laboratory or present a paper at an international conference.

• Close ties are maintained with other materials research laboratories (iThemba LABS, Mintek, Stellenbosch University, CSIR, Wits University, Pretoria University, Nelson Mandela University), and our postgraduate students frequently make use of equipment facilities at these institutions.

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1.7 Research infrastructure and facilities

The equipment base in the Centre for Materials Engineering has been developed over a number of years to underpin the research carried out. Since we are concerned with the physical, chemical, electrical and mechanical properties of ceramic, polymeric, metallic and composite materials, the equipment ranges from microscopes to investigate the fine microstructure to large mechanical testing equipment. The Centre for Materials Engineering is very well equipped with materials testing facilities, both of a commercial nature and custom-built for specific simulation testing. Since many items of equipment exist in the Centre, it is convenient to divide them into the following equipment suites:

• Metallographic Preparation.

• Microscopy (including several light microscopes and access to the electron microscope suite in the UCT EM Unit).

• Heat Treatment furnaces.

• Thermal Analysis including dilatometry, scanning calorimetry and thermogravimetric analysis.

• Mechanical Testing including a range in screw-driven and hydraulic universal testing machines (loadcell capacity from 5kN to 250kN).

• Hardness Testing (2g – 150kg load) and high/low energy impact testing.

• Corrosion Testing.

• Creep testing

In order to demonstrate our commitment to develop and maintain modern research facilities, listed below are a number of equipment or accessory items acquired during the period under review. The majority of funding for these relatively expensive items was sourced externally.


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1.1.1 Additional EBSD system

A new Oxford EBSD Aztec system was acquired as part of a funding grant to our Electron Microscope Unit to install a new TESCAN scanning electron microscope. We now have two Oxford EBSD systems available in our Electron Microscope Unit. The new system provides even better resolution which is necessary for our work on deformed metallic materials.

1.1.2 Upgrade of digital weighing system on existing STA 409 Thermal Analyser

The existing Netzsch Thermal Analyser (Netzsch STA409) was purchased approximately 15 years ago and has by all accounts provided very good service across a broad range of materials research activities within the Centre for Materials Engineering. The upgrade solved the weakness in the machine relating to the thermo-gravimetric (TG) technique which has suffered with poor resolution. This situation has been significantly improved by upgrading the TG module to incorporate a digital weighing system which now provides better resolution and stability. Included in this upgrade is the addition of a refrigerated bath water circulator which allows precise control of the external temperature of the STA409 machine.

1.1.3 Metallurgical Microscope :Nikon Eclipse MA 200

A modern wide-field incident light research microscope has been added to our suite of light microscopes. This machine complements the Reichert MEF3 microscope but provides better wide-field optics.

1.7.4 Struers Tenupol jet polisher and upgrade to fume hood for perchloric acid use

In order to expand our ability to prepare TEM foils by jet polishing, we acquired a new Struers Tenupol jet polishing facility incorporating a controlled refrigeration unit. It was also necessary to upgrade our fume hood to accommodate the use of perchloric acid for jet polishing.

1.7.5 Thermal camera

A high temperature thermal camera was acquired for use with the Gleeble 3800 thermo-mechanical test facility. Although we use thermocouples to control and measure temperature on specimens during thermo-mechanical testing, the exact thermal profile of the specimen is often required, particularly during assessment of strain localisation in weldments. The thermal camera now provides sufficient resolution and range to map out the temperature of the entire test specimen.

1.7.6 Integrated strain sensor system on Zwick UTM

This system integrates and synchronises external sensor measurements, such as strain gauges, with the existing force and displacement measurements on our Zwick UTM test frame. This allows for conducting material characterisation tests that are fully compliant with the ASTM standards, and creates opportunities for additional measurements that add valuable data to each experiment.

1.7.1

1.7.2

1.73

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1.8 Interdisciplinary and collaborative research

The Centre operates on an “open-door” approach for researchers and students requiring materials research input, but endeavours to ensure cost recovery wherever possible. Consequently, we are able to assist many researchers outside of the Centre with regard to equipment utilisation and interpretation of materials analysis. In many instances this may lead to the initiation of collaborative research as the projects develop. More specifically, the Centre plays a strong supporting role with respect to allied research activities within the Mechanical Engineering Department. This is particularly manifest during the course of the final year undergraduate projects that represent the capstone course for the mechanical engineering, and mechanical and mechatronic engineering undergraduate programmes. At least ten candidates per year elect to work on projects that utilise the Centre’s resources extensively. A number of these projects often progress to MSc level. However, access to our laboratories and equipment facilities is not restricted to students and researchers in our Mechanical Engineering Department. We have during the current reporting period assisted students in the health sciences, biological sciences, geology, and civil and chemical engineering.

There are a number of very strong collaborative research activities within South Africa and a growing number in the international arena. Brief details are as follows:

1.8.1 UCT Health Sciences Faculty

Drs Keith Hoskin and Thomas Hilton of the UCT Health Sciences Faculty are participating in the PhD project that investigates the surface treatment of titanium alloys to combat bacterial infection as a result of titanium alloy prosthetic implantation. They are assisting with the final stage of the research which involves in-vitro antibacterial testing in order to evaluate the effectiveness of the proposed surface modifications.

1.8.2 Stellenbosch University (SUN)

Dr Thorsten Becker of the SUN Department of Mechanical and Mechatronic Engineering is a key member of our EPPEI Materials and Mechanics specialisation. As a result of his expertise in fracture mechanics and damage measurement using digital image correlation, he is a regular co-supervisor for students registered at UCT through the EPPEI programme. In addition, he also supervises postgraduate students registered at SUN who contribute strongly to the objectives and research thrust in the EPPEI Materials and Mechanics specialisation hosted at the UCT Centre for Materials Engineering.

1.8.3 CSIR Aeronautics Division

Dr Glen Sneddon of the Council for Industrial and Scientific Research (CSIR) is a research partner in the MSc project aimed at assessing the performance of nickel based super alloys produced via the selective laser melting (SLM) practice. This collaboration includes interaction with Mr Nana Arthur of the CSIR-National Laser Centre who are party to manufacturing the nickel-based super alloy components that will be tested and characterised at our Centre.

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1.8.4 Warwick Manufacturing Group

Dr Sarah George of the UCT Centre for Materials Engineering and Professor Barbara Shollock of the Manufacturing Group at Warwick University have expressed interest in the initiation of research collaboration with regard to the design of aluminium alloys for application in the automotive industry.

1.8.5 CSIR Light Metals Division

The Centre has a long standing collaboration (since about 2002) with the Light Metals Division at the CSIR in Pretoria. Our Centre is a strong partner in the research thrust supported by the Department of Science and Technology through the Advanced Metals Initiative (AMI) and particularly the Titanium Centre of Competence. We are currently involved jointly in research on titanium direct powder rolling.

1.8.6 Cooperative Programme in Additive Manufacturing (CPAM)

CPAM was initiated by the Department of Science and Technology (DST) to develop competency in additive manufacturing in South Africa, particularly with respect to component manufacture for the aeronautical and medical industries. Our Centre is a principal member of the consortium which includes the CSIR-National Laser Centre, Central University of Technology (Bloemfontein), Stellenbosch University, Vaal University of Technology, and North West University (Potchefstroom). Our role in this consortium focuses on component integrity assessment and optimisation of mechanical properties for titanium alloys.

1.8.7 EPPEI Component Life Cycle Management Inter-university Programme

In parallel to the main thrust of the EPPEI Materials and Mechanics specialisation, our Centre leads the inter-university programme in component life cycle management (CLCM) and includes participation with the School of Chemical and Materials Engineering (Wits University), Department of Mechanical Engineering (Wits University), Department of Materials Science and Metallurgical Engineering (Pretoria University), and the Department of Mechanical Engineering (Nelson Mandela University). The aim of this programme is to advance techniques and methodologies to improve the ability to predict and manage critical component life on the Eskom coal-fired power stations. This programme remains student centric and student recruitment and research proposals are coordinated through the EPPEI Materials and Mechanics specialisation hosted at our Centre.

1.8.8 Centre for High Resolution Transmission Electron Microscopy (CHRTEM), Nelson Mandela University

Our collaboration and engagement with the CHRTEM at the Nelson Mandela University in Port Elizabeth is multi-facetted. Not only are they an integral partner to the EPPEI Materials and Mechanics Specialisation, and consequently provide direct support for advanced materials characterisation within the EPPEI Materials and Mechanics research activities, but several of our students working within the different research themes in our Centre make use of the extensive microscopy facilities and expert staff at the CHRTEM on a regular basis.

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1.8.9 Department of Mechanical Engineering, University of Glasgow

We are presently engaged in two projects with Dr Andrew McBride at the University of Glasgow. Dr Sarah George is collaborating with Dr McBride on the project which deals with the modelling the hot roll roughing stage of can-body stock. This project directly supports the MSc at UCT which is investigating the effect of homogenisation practices on intermetallic content and subsequent influence on hot roll forces during the first stage rough rolling process. The second project involves support provided by our Centre in the form of in-house hot deformation testing to simulate certain aspects of friction stir welding of nickel based super alloys.

1.8.10 Centre for Electron Microscopy and Analysis (CEMAS), Ohio State University

Our interactions with Professor Hamish Fraser at Ohio State University commenced in 2011 and since this time he has provided input into the design of a number of our research projects that deal with titanium alloys. Professor Fraser has visited us on a number of occasions and he hosted one of our PhD students for a period of six weeks in mid-2017 during which time the student gained experience working on electron microscopes with scientists at CEMAS.

1.9 Staff and succession planning

The core activities within the Centre are developed and supervised by academic staff who are employed within the Mechanical Engineering Department. Consequently responsibilities rest with undergraduate programme delivery, postgraduate research supervision and administration as it pertains to both the greater Department and the Centre. This situation is emphasised even further for the Director who takes care of the Centre staff, facilities, research supervision, and plays a major role in fund raising. During the past 5 years (1 April 2013 – 31 March 2018) the director was also appointed to the HoD position in the Mechanical Engineering Department. This arrangement placed some strain on the leadership in the Centre and the ability of the director to devote sufficient time to research and research publication output in particular. Nevertheless, with recruitment of additional staff along the way we have managed, but we would like to see more attention directed at publication output going forward. We are also very fortunate to receive highly valuable and critical input from a number of visiting/part-time lecturers (see front page for details) who contribute towards the BSc(Hons) programme and co-supervision of postgraduate research students.

1.9.1 New staff developments

The Eskom EPPEI programme, and in particular the establishment of the EPPEI Materials and Mechanics Specialisation in our Centre, has provided opportunities to recruit additional research and support staff. Professor Bernhard Sonderegger joined us at the beginning of 2013 as leader of the EPPEI Materials and Mechanics Specialisation on a 5-year contract appointment. His appointment provided excellent opportunity for direct engagement with Eskom and he supervised a number of Eskom engineers who joined us as full-time postgraduate students. Unfortunately, and for personal reasons, he resigned from the position at the end of 2014 and re-joined the Technical University of Graz. Nevertheless, his short appointment gave us good opportunity to get the EPPEI Materials and


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Mechanics Specialisation off the ground and to establish the firm collaboration and participation by the Centre for High Resolution Transmission Electron Microscopy at Nelson Mandela University.

Further new staff appointments during the current review period are as follows:

1.9.1.1 Dr Sarah George – senior lecturer appointed to a permanent position in the Mechanical Engineering Department from 1 January 2013. As is evident from this review portfolio, Dr George is a full member of our Centre and engaged in light metal research in particular.

1.9.1.2 Dr Richard Curry – appointed to a contract senior research officer position in our Centre from 1 March 2018 – 28 February 2022. Dr Curry participated in a part-time capacity since mid-2016 and specifically engaged with the EPPEI Materials and Mechanics Specialisation. His full-time role over the next four years will grow the EPPEI Materials and Mechanics research activities and in particular he brings expertise within the mechanics focus area.

1.9.1.3 Dr Chris Woolard – appointed to a part-time senior lecturer position in the Mechanical Engineering Department since 1 January 2017. Dr Woolard’s responsibilities lie in convening the BSc(Hons) in Materials Science programme and pursuing research in polymeric and composite materials.

1.9.1.4 Mrs Soraya von Willingh – appointed to a contract scientific officer position from 1 September 2017 – 31 August 2022. Mrs von Willingh’s role is to provide technical and laboratory support to students registered on the EPPEI Materials and Mechanics programme. In addition, she also provides basic administration support to the Centre and assistance with the general oversight of the laboratories.

1.9.1.5 Dr Johan Westraadt – senior research officer at Nelson Mandela University. As described earlier in this report, we fully support the appointment of Dr Westraadt at the Centre for High Resolution Transmission Electron Microscopy (CHRTEM) through funding provided for the EPPEI Materials and Mechanics Specialisation. This appointment is particularly focused on supporting materials characterisation in our research, and relevant research supervised at Nelson Mandela University as part of the EPPEI Materials and Mechanics Specialisation.

1.10 BSc(Hons) in Materials Science programme

The BSc(Hons) programme in Materials Science was initiated by the Centre and commenced with the first intake of 8 candidates in 2004. The objective of the programme is two-fold: (i) to develop more graduates who have general skills in materials science, and (ii) to provide a feeder for candidates to register for the MSc research degree in materials engineering. This programme has proved to be highly successful on both accounts and we have recruited and graduated a steady flow of candidates since 2004. See Table on page 39 for intake and graduation numbers during the current review period.

Although the BSc(Hons) programme forms part of the suite of programmes offered in the Mechanical Engineering Department, the full governance of the programme rests within the Centre for Materials Engineering. The programme is presented by the core team members of the Centre and a team of part-

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time/visiting lecturers who are able to supplement the syllabus with their particular specialisations (see front page for list of visiting lecturers/researchers). We are also highly fortunate in that the UCT Chemical Engineering Department has participated in the lecturing programme since 2017. This involvement has also led to our ceramics materials course being included as a 4th year elective for students registered for the BSc(Eng) in Chemical Engineering programme. In many instances the courses are specific to the Honours programme (e.g. generic materials courses including metals, ceramics, polymers and composites), but the students also attend courses which are offered in the mainstream mechanical engineering programme.

2: Quality of research output

Our research approach is aimed at providing an opportunity to develop new knowledge, educate students in research skills, and assist industry by way of appropriate knowledge transfer. Consequently, our research output can be measured in terms of formal publication output (dissemination of knowledge in a public way), number of students qualifying for higher degrees, and the extent of interaction with the local manufacturing industry, and in recent years, the electricity power industry represented by Eskom. The list of Publications during the current review period is provided on page 40. Our research activity is undoubtedly student centric and in fact our general philosophy is to seek NRF, UCT, THRIP and industrial sponsorship to support postgraduate students and associated running costs rather than focussing on recruiting human resource to perform industrial research. See Table on pages 38 & 39 which summarises postgraduate qualifiers during the current review period. However, it is acknowledged that the latter situation does arise from time to time. Thus it may be said that a self-defined goal is being able to attract suitable funding to support a cohort of postgraduate students so that a high level of research can be conducted that will manifest in international quality research output and highly trained personnel. It goes without saying that our own personal measure of success includes publication record and corresponding NRF rating level.

We believe that our output is good and consistent in all aspects described above. As individuals we strive for improved NRF ratings and therefore it is acknowledged that there is always room for improvement. As mentioned earlier in this report, the director who is an established researcher in the Centre, has found it difficult to contribute to publication output during the current period under review as a result of the demands placed on his role as the HoD of the Mechanical Engineering Department. It is intended that this situation will improve significantly going forward and there is substantial postgraduate student output during the past five years that can be translated to publications. Our throughput of postgraduate students is good, but once again improvements in throughput rate would be welcomed. The funding landscape by the NRF has changed over recent years. On the positive side, students are able to attract bursary support directly from the NRF although this does not support non-South African students. In addition, it is possible to obtain meaningful funding from the NRF as a non-rated researcher in the form of Thuthuka funding and we have been quite successful in this regard during the current review period. These positive aspects will impact on publication and student output. The move of the THRIP funding (previously granted by the Department of Science and Industry and administered by the NRF) to the Department of Trade and Industries does present new challenges Industries. We are still finding our way through this new process and hope to be able to attract THRIP funding in the near future.


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3: Research capacity development

Research capacity in materials science and engineering is influenced by academic expertise and laboratory and equipment infrastructure. The latter is particularly critical in our field and requires appropriate laboratory space and high quality modern equipment. To this end a considerable amount of effort is directed at growing and maintaining our infrastructure (see section 1.7). Furthermore, the Centre employs a senior technical officer who is responsible for the management and supervision of all the Centre’s facilities. In this way our laboratories and equipment are maintained in good order and we are able to provide a fully functional research environment at all times. The Centre also relies heavily on access to the facilities at the UCT Electron Microscope Unit and we play a supportive role in acquiring equipment and maintaining this important centralised University facility. We also take advantage of facilities available within the region, e.g. iThemba LABS Materials Research Division and the Electron Microscope Unit at the University of the Western Cape. As already described previously, our strong relationship with the Centre for High Resolution Transmission Electron Microscopy at the Nelson Mandela University has contributed substantially to our progress in materials characterisation.

The Eskom funded EPPEI Materials and Mechanics Specialisation, which is hosted within our Centre, has provided excellent opportunity to enhance our research capacity. The recent appointment of Dr Curry and Mrs von Willingh, and the ongoing participation by Dr Johan Westraadt of the Nelson Mandela University, will provide much greater capacity to not only recruit more postgraduate students, but also translate our research into viable industry solutions and high quality publication output. Furthermore, if we are successful with our new proposal to Hulamin Rolled Products we will also have access to a part-time programme manager in aluminium research, who will not only improve our interaction with industry, but also support postgraduate students in thermo-mechanical processing of aluminium wrought products.

2012

Nick Clinning Thermomechanical processing of blended elemental powder Ti-6Al-4V alloy RD Knutsen

Chetan Chhiba Titanium alloy powder production from waste metal RD Knutsen

Tokoloho Rampai Synthesis of Ti2AlC, Ti3AlC2 and Ti3SiC2 MAX phase ceramics; and their composites with c-BN

CI Lang

Craig Knowles Residual stress measurement and structural integrity evaluation of SLM Ti-6Al-4V RB Tait

2013

Khanyisa Mabunda Discovering Novel Platinum Structures CI Lang

William Makheta Phase transformations in Platinum-based coatings CI Lang

Soraya Allies Investigation of a computationally predicted structure in the Ag-Pt system CI Lang

Graham Morrison The Effect of Stabilisation Heat Treatment on AA5182 Aluminium Alloy SL George

Irenee Kaminuza Thermal and chemical analysis of carbonaceous materials: diesel soot and diesel fuel reactor deposits

CD Woolard

Velile Vilane Grain refinement in cast Ti-6Al-4V by hydrogenation deformation and recrystallisation

RD Knutsen

2014

Philip van der Meer Effect of geometry on the microstructural ageing of a 1CrMoV turbine rotor steel RD Knutsen and B Sonderegger

Teboho Molokwane Quantification of creep damage on creep aged 12CrMoV121 (X20) after maintenance welding.

RD Knutsen and B Sonderegger

Nasheeta Hanief Phase Transformations in the Platinum Chromium coated system M Topic

Luke Finklestein Novel Ordering of Platinum Alloys CI Lang

Rutendo Matengaifa Atomistic Modelling of Pt and Alloy Systems CI Lang

Nadeem Gamiet Numerical analysis of compressive residual stresses in metallic materials as a result of shot peening

RD Knutsen and T Becker

Tapiwa Tevera Evaluation of Corrosion Behaviour of Zinc and Zinc-Aluminium Coatings using Field and Laboratory Tests

RD Knutsen

2015

Nur Mohamed Fatigue properties of Titanium RB Tait

Yu David Zhang Development of direct powder rolling process route for Ti-6Al-4V RD Knutsen

Chase Hyde Optimisation of thermo-mechanical processing for aluminium can-body stock RD Knutsen and SL George

Clinton Leary Fabrication of PtNi and PtV Near-Surface Alloys as Improved Catalysts for Proton CI Lang

Lwazi Qangule Influence of process route on mechanical property development in sintered Commercially Pure (CP)-Ti and Blended Elemental (BE)-Ti

RD Knutsen

Uyuenendiwannyi Mandavha

Analysis of carbonaceous solid deposits from thermal stressing of FAMEs and FAME/diesel blends at different temperatures in a continuous flow reactor

CD Woolard

2016

Muhammad Stracey Modelling of dislocation creep in 9-12% chromium steels RD Knutsen

Royden Weyer Modelling of damage due to diffusional creep in high chromium steels RD Knutsen

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List of Masters Projects


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2017

Leebashan Naicker Influence of heat treatment condition on the stress corrosion cracking properties of low pressure turbine blade steel FV520B

RD Knutsen

Pedro Chicuba Assessment of the Pitting and Crevice Corrosion Resistance of Alloy 825 in Stagnant Seawater

RD Knutsen

Trisha Rasiawan Weldability limits for creep aged material RD Knutsen

Duduzile Nkomo The effect of processing and microstructure on the corrosion behaviour of Hercules™ + Mo stainless steel

RD Knutsen

Bridget Sikhondze Steckel Mill Rolling Simulation of Ti6Al4V Alloy SL George and RD Knutsen

Rabelani Masindi The influence of steckel mill process parameters on dynamic and static annealing response of AISI430 ferritic stainless steel

RD Knutsen and SL George

Livhuwani Magidi The Study of Intermetallic Particles in Aluminium Alloy AA3104 Can-Body Stock SL George

Alex Becker The effect of laser shock peening and shot peening on the fatigue performance of aluminium alloy 7075

RB Tait and SL George

Nicole Seumangal Influence of the heat treatment procedure on the stress corrosion cracking behaviour of low pressure turbine blade material FV566

RD Knutsen and B Sonderegger

2018

Oliet Tshmano Development of the small punch test platform to evaluate the embrittlement of power plant materials

RD Knutsen and T Becker

Francisco Agostinho Development of High Performance and Efficient Coating Repair Systems for Offshore Tropical Marine Environment

RD Knutsen

BSc(Hons) students registered vs students graduated (2012-2017)

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JOURNAL PUBLICATIONS

• SL George and RD Knutsen, Composition segregation in semi-solid metal cast AA7075 aluminium alloy, Journal of Materials Science, 11, (2012), 4716–4725.• M Theron, RD Knutsen, L Ivanchev and H Burger, Effect of heat treatment on the properties of laser-beam welded rheo-cast F357 aluminium, Journal of Materials Processing Technology, 212, (2012), 465–470.• SL George and RD Knutsen, Evolution of the solidification microstructure of rheocast high purity aluminium, Solid State Phenomena, 192-193, (2013), 109-115.• G Leteba, RR Vanfleet and CI Lang, Synthesis of V, Pt and Pt-V nanoparticles, International Journal of Nanoparticles, 6, (2013), 282-295.• G Leteba and C I Lang, Synthesis of bimetallic platinum nanoparticles for biosensors, Sensors, 13, (2013), 10358 – 10369.• KP Mabunda and CI Lang, The Pt8Zr ordering transformation, Journal of Alloys and Compounds, 613, (2013), 375-378.• T Rampai, CI Lang and I Sigalas, Investigation of MAX phase/c-BN composites, Ceramics International, 39 (5), (2013), 4739-4748.• V Vilane and RD Knutsen, Grain refinement in cast Ti-6Al-4V by hydrogenation, deformation and recrystallisation, Materials Science Forum, 753, (2013), 271-274.• MR Ahmadi, E Povoden-Karadeniza, B Sonderegger, KI Öksüzc, A Falahatic, E Kozeschnika, A model for coherency strengthening of large precipitates, Scripta Materialia, 84–85, (2014), 47–50.• MR Ahmadi, B Sonderegger, E Povoden-Karadeniz, A Falahati, E Kozeschnik, Precipitate strengthening of non-spherical precipitates extended in ⟨100⟨ or {100} direction in FCC crystals, Materials Science and Engineering A, 590, (2014), 262–266.• VN Vilane, RD Knutsen and JE Westraadt, Submicron grain size formation in thermo-hydrogenated and deformed Ti-6Al-4V: The effect of processing route on the degree of grain refinement, Advanced Materials Research, 1019, (2014), 266-272.• C Mshumi, CI Lang, LR Richey, KC Erbb, CW Rosenbrockb, LJ Nelson, RR Vanfleet, HT Stokes, BJ Campbell, GLW Hart, Revisiting the CuPt3 prototype and the L13 structure, Acta Materialia, 73, (2014), 326–336.• B Vrancken, V Cain, R Knutsen, J Van Humbeeck, Residual stress via the contour method in compact tension specimens produced via selective laser melting, Scripta Materialia, 87, (2014), 29–32.V Cain, L Thijs, J Van Humbeeck, B Van Hooreweder, RD Knutsen, Crack propagation and fracture toughness of Ti-6Al-4V alloy produced by selective laser melting, Additive Manufacturing, 5, (2015), 68-75.• SL George and C Mias, Effect of rolling temperature on annealing of AA1050 aluminium alloy, Materials Science Forum, 828-829, (2015), 200-205.• VN Vilane, RD Knutsen and JE Westraadt, Contribution of hydrogen promoted aluminium partitioning to tempered martensite embrittlement in Ti-6Al-4V, Materials Science Forum, 828-829, (2015), 181-187.• SD Yadav, B Sonderegger, B Sartory, C Sommitsch, C Poletti, Characterisation and quantification of cavities in 9-Cr martensitic steel for power plants, Materials Science and Technology, 31 (5), (2015), 554-564.• SD Yada, B Sonderegger, M Stracey and C Poletti, Modelling the creep behaviour of tempered martensitic steel based on a hybrid approach, Materials Science and Engineering: A, 662, (2016), 330-341.• GLW Hart, LJ Nelson, RR Vanfleet, BJ Campbell, MHF Sluiter, JH Neethling, EJ Olivier, S Allies, CI Lang, B Meredig and C Wolverton, Revisiting the revised Ag-Pt phase diagram, Acta Materialia, 124, (2017), 325 – 332.• RP Matthews, RD Knutsen, JE Westraadt and T Couvant, Intergranular oxidation of 316L stainless steel in the PWR primary water environment, Corrosion Science, 125, (2017), 175-183.• J McGuire, R Govender, P Park-Ross, J Fagan, The Endolaryngeal anterior commissure stent – Cheap and easy, The Laryngoscope, 127 (8), (2017), 1869–1872.

REFEREED CONFERENCE PAPERS AND EXTENDED ABSTRACTS

• TJ Molokwane, B Sonderegger, RD Knutsen, JE Westraadt, M Bezuidenhout and P Doubell. Microstructural and property assessment of creep aged 12Cr Steel after welding, In Proc. 3rd International ECCC – Creep & Fracture Conference, Rome, May 5-7, (2014).• PT van der Meer, B Sonderegger, RD Knutsen, JE Westraadt and M Bezuidenhout, Effect of geometry on the microstructural ageing of a 1CrMoNiV turbine rotor steel, In Proc. 3rd International ECCC – Creep & Fracture Conference, Rome, May 5-7, (2014).• SL George and C Mias, Effect of rolling temperature on annealing of AA1050 aluminium alloy. In Proceedings International Light Metals Technology Conference, (2015), 200-205.• N Clinning and RD Knutsen, Phase identification in Ti-6Al-4V using microscopy. In Proceedings of the Microscopy Society of Southern Africa, 42, (2012), 77.• G Morrison, SL George and RD Knutsen, The effect of stabilisation heat treatment on AA5182 aluminium alloy. In Proceedings of the Microscopy Society of Southern Africa, 42, (2012), 78.

• TS Tevera and RD Knutsen, Evaluation of corrosion behaviour of Zn-10Al alloy coating on low carbon steel wire. In Proceedings of the Microscopy Society of Southern Africa, 42, (2012), 81.• TJ Molokwane, B Sonderegger, RD Knutsen and JE Westraadt, Microstructural and property evaluation of creep aged 12Cr steel after welding. In Proceedings of the Microscopy Society of Southern Africa, 43, (2013), 68.• RR Masindi, RD Knutsen and SL George, Microstructural evolution in AISI430 stainless steel during austenite to ferrite transformation. In Proceedings of the Microscopy Society of Southern Africa, 43, (2013), 69.• VN Vilane, RD Knutsen and JE Westraadt, Microstructure evolution in Ti-6Al-4V during hydrogenation and deformation processing. In Proceedings of the Microscopy Society of Southern Africa, 43, (2013), 73.• BG Sikhondze, SL George and RD Knutsen, Steckel mill rolling simulation on Ti-6Al-4V alloy. In Proceedings of the Microscopy Society of Southern Africa, 43, (2013), 74.• VN Vilane, RD Knutsen and JE Westraadt, Variant selection during hydrogen affected b- to a-phase transformation in Ti-6Al-4V alloy. In Proceedings of the Microscopy Society of Southern Africa, 43, (2013), 75.• RD Knutsen, B Sonderegger, P van der Meer, JE Westraadt and SL George, Statistical aspects of grain size analyses of EBSD maps. In Proceedings of the Microscopy Society of Southern Africa, 43, (2013), 79.• G Morrison, SL George and RD Knutsen, The effect of stabilisation heat treatment on AA5182 aluminium alloy. In Proceedings of the Microscopy Society of Southern Africa, 43, (2013), 72.• LT Magidi, SL George and RD Knutsen, Quantitative and qualitative analysis of intermetallic particles in aluminium alloy AA3104 can-body stock during homogenisation. In Proceedings of the Micros copy Society of Southern Africa, 44, (2014), 96.• RR Masindi, SL George and RD Knutsen, The influence of austenite volume fraction on recrystallization kinetics of AISI430 stainless steel. In Proceedings of the Microscopy Society of Southern Africa, 44, (2014), 77.• V Vilane, RD Knutsen and JE Westraadt, Embrittlement in Ti-6Al-4V due to hydrogen induced aluminium enrichment. In Proceedings of the Microscopy Society of Southern Africa, 44, (2014), 68.• RP Matthews, RD Knutsen and JE Westraadt, Oxidation of 316L stainless steel in the pressurised water reactor environment. In Proceedings of the Microscopy Society of Southern Africa, 46, (2016), 9.• VN Vilane, RD Knutsen and JE Westraadt, Microstructure and tensile property evolution in hydrogenated-dehydrogenated (HDH) Ti-6Al-4V. In Proceedings of the Microscopy Society of Southern Africa, 46, (2016), 45.• KA Käfer, SL George and RD Knutsen, Influence of processing parameters on the microstructure and texture of commercial Ti-6Al-4V alloy. In Proceedings of the Microscopy Society of Southern Africa, 46, (2016), 46.• C Mias, SL George and RD Knutsen, Effect of processing parameters on microstructure and texture evolution during reverse mill rolling of AA3104. In Proceedings of the Microscopy Society of Southern Africa, 46, (2016), 47.• H Naicker and RD Knutsen, Assessment of homogenisation progress in sintered direct powder rolled Ti-6Al-4V strip. In Proceedings of the Microscopy Society of Southern Africa, Vol. 47, (2017), 9.• KA Käfer, RD Knutsen and SL George, Effect of strain rate and temperature on the microstructure and texture development in Ti-6Al-4V alloys. In Proceedings of the Microscopy Society of Southern Africa, 47, (2017), 22.• I Vazirgiantzikis and SL George, The effect of silver ion implantation on the surface morphology of polished and anodised titanium surface. In Proceedings of the Microscopy Society of Southern Africa, 47, (2017), 45.• AC Carlisle and SL George, The effect of laser shock peening on fatigue properties of various materials. In Proceedings of the Microscopy Society of Southern Africa, 47, (2017), 44.• S Baron and SL George, The role of homogenisation conditions on intermetallic particle fragmentation during breakdown rolling of AA3104 aluminium alloy. In Proceedings of the Microscopy Society of Southern Africa, 47, (2017), 47.

REFEREED UNPUBLISHED CONFERENCE PROCEEDINGS

• Y Zhang and RD Knutsen, Parametric study of the influence of process variables on direct powder rolling for CP-titanium and stainless steel. In Proceedings of the Advanced Metals Initiative Nuclear Materials Development Network Conference, (2015), Port Elizabeth, 183-192.• RR Masindi, SL George and RD Knutsen, The influence of Steckel mill hot rolling parameters on the microstructure evolution of AISI430 ferritic stainless steel. In Proceedings of the Advanced Metals Initiative Nuclear Materials Development Network Conference, (2015), Port Elizabeth, 177-182.• L Magidi, SL George and RD Knutsen, Evolution of intermetallic particles in aluminium alloy AA3104 during homogenisation. In Proceedings of the Advanced Metals Initiative Nuclear Materials Development Network Conference, (2015), Port Elizabeth, 35-41.


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